Method for cleaning quartz epitaxial chambers

ABSTRACT

A method of cleaning an epitaxial reaction chamber in-situ is disclosed. The method may include a pre-coating step, a high temperature baking step, and a gas etching step. The method is able to remove residue buildup within the reaction chamber, which may be made of quartz.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional of, and claims priority to and the benefit of, U.S. Provisional Patent Application No. 62/859,621, filed Jun. 10, 2019 and entitled “METHOD FOR CLEANING QUARTZ EPITAXIAL CHAMBERS,” which is hereby incorporated by reference herein.

FIELD OF INVENTION

The invention relates to a reaction system for processing semiconductor substrates. Specifically, the invention relates to cleaning the reaction system after a formation of chemical residue takes place on internal walls of the reaction system.

BACKGROUND OF THE DISCLOSURE

Epitaxial processes are known to be employed in particular semiconductor applications, like NMOS devices for example. These processes utilize chemical precursors that generally have a propensity to form a thick residue coating on chamber walls of the reaction system. The chamber walls are typically made of quartz due to quartz's properties of low impurities, robustness with heated chemistries, and transparency.

It is imperative that the residue formed on the quartz walls be removed from time to time. The residue may adversely affect formation of epitaxial films due to the introduction of thermal drift, particle contamination, and/or high dopant background concentrations. In some instances, the residue may obstruct the passage of thermal energy from heating source to wafer; ultimately leading to process drift and/or film uniformity loss. Particles generated from the residue are likely to shed, and may result in film defects. There is also the likelihood of outgassing from the residue during process. In the event there is a coating upstream of the wafer, the produced gas may interfere with the dopant profile of the wafer. Further, outgassing from the residue makes periodic maintenance activities difficult because of the toxicity of the gas.

Previous approaches to cleaning quartz walls may involve removal and replacement of the reaction chamber. However, this requires the tool to be shut down, leading to reduced throughput and probability of process shift. As a result, a process that performs the cleaning in-situ is preferred. Prior approaches have utilized a plasma generated in-situ to form the cleaning gas, as described in U.S. Pat. No. 6,749,717, entitled “Device for In-situ Cleaning of an Inductively-coupled Plasma Chambers,” hereby incorporated by reference. However, plasma generators may generate cleaning gas that may also detrimentally etch the chamber walls. Alternatively, a commonplace cleaning solution may be heating the reaction chamber in the presence of gaseous HCl flow. The main drawback from this approach is that typically, the peripheral regions of the reaction chamber cannot get hot enough to have a sufficient etch.

Removal of silicon-containing materials are disclosed in U.S. Pat. No. 8,445,389, entitled “Etchant Treatment Processes for Substrate Surfaces and Chamber Surfaces,” hereby incorporated by reference. However, the epitaxial processes may result in residues more difficult to remove than the silicon-containing materials.

As a result, a need exists for a process that allows for effective removal of residue generated in epitaxy applications from walls in a reaction chamber without adversely affecting the walls.

SUMMARY OF THE DISCLOSURE

A method for in-situ cleaning a reaction chamber is disclosed. The method comprises: pre-coating a plurality of walls within a reaction chamber with a protective coating gas, the protective coating gas comprising at least one of: dichlorosilane (DCS), silane, or disilane; heating the reaction chamber to a temperature exceeding 700° C.; and flowing an etchant gas into the reaction chamber; wherein the etchant gas removes a residue from the plurality of walls, the residue comprising at least one of: arsenic, phosphorous, or germanium-based material.

For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures, the invention not being limited to any particular embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

These and other features, aspects, and advantages of the invention disclosed herein are described below with reference to the drawings of certain embodiments, which are intended to illustrate and not to limit the invention.

FIG. 1 illustrates a flow chart of a cleaning process according to at least one embodiment of the invention.

FIG. 2 illustrates a chamber capable of running a process according to at least one embodiment of the invention.

It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below.

Processes for forming NMOS devices may form films such as group 5 layers or a combination thereof. To accomplish this, the processes may use chemical precursors such as arsine or phosphine, or any halogenated or alkyl-substituted variant thereof. The residue may comprise arsenic, phosphorous, arsenic compounds (AsX_(n)), phosphorous compounds (PX_(n)), arsenic trichloride, arsenic dichloromonohydride, or phosphorous chloride, for example. For residues involving chemicals like arsenic, for example, the residue can cause serious health problems to equipment engineers during tool maintenance. Embodiments of the invention are directed to minimize the presence of arsenic, phosphorous, and germanium chemicals and compounds to near zero concentrations to meet standards set by the American Conference of Governmental Industrial Hygienists threshold value limits for the occupational exposure limit. These concentrations may be met in less time, in approximately 10 to 60% of existing outgassing wait times, allowing for greater productivity. Owing to complete coating removal, the equipment engineer's exposure to dust and residue is also greatly reduced. Following the clean, arsine and chlorine on the equipment engineer is below the occupational exposure limit of 0.005 and 0.5 parts per million (ppm), respectively.

Furthermore, embodiments of the invention are directed to increasing the lifetime of quartz chambers before they would need to be either replaced or refurbished. Embodiments of the invention could allow for potentially as many as 10,000 to 30,000 wafers to be processed prior to replacement. Such an extension in chamber lifetime is critical given industry shortages in quartz chamber availability.

FIG. 1 illustrates a process 100 in accordance with at least one embodiment of the invention. The process 100 comprises: (1) a protective pre-coating step 110; (2) a high temperature baking step 120; and (3) a gas etching step 130. The protective pre-coating step 110 may be required depending on a gas used in the gas etching step 130. The protective pre-coating step 110 may be used to protect parts within the reaction chamber. For example, particular parts in the reaction chamber may be made of silicon carbide (SiC) or graphite. Prolonged exposure to particular gaseous halides may result in damage to the SiC or graphite parts. The protective pre-coating step 110 would prevent this damage from prolonged exposure.

The protective pre-coating step 110 may comprise a flow of a chemical precursor, such as at least one of: dichlorosilane (DCS), trichlorosilane (TCS), silane (SiH₄), or disilane (Si₂H₆). The chemical precursor would form a layer onto the SiC or graphite parts of the chamber as well as the quartz walls. The temperature of the reaction chamber during the protective pre-coating step 110 may range between 750-950° C. The protective pre-coating step 110 may continue until a layer of the precursor forms a thickness exceeding 35 nm, 40 nm, or 45 nm. The duration of the protective pre-coating step 110 may exceed 180 s, 210 s, or 240 s.

The high temperature baking step 120 comprises heating the reaction chamber to temperatures in excess of 700° C., 800° C., or 900° C. The reason for the high temperature baking step 120 may include heating the reaction chamber, especially at peripheral regions, to enable effective etching chemistry. The high temperature bake step may also add in decoupling the susceptor temperature from that of the chamber. The duration of the high temperature baking step 120 may exceed 160 s, 170 s, or 180 s. The high temperature baking step 120 results in a hot quartz chamber, which may result in an easier removal of the residue during the gas etching step 130.

The gas etching step 130 may comprise flowing a gas including at least one of: chlorine (Cl₂) or nitrogen (N₂). In those situations where chlorine is used, this would obviate the need for hydrochloric acid (HCl) within the chamber, leading to safer conditions for operators of the tool. The pressure of the gas etching step 130 may range between 40-100 Torr, 45-90 Torr, or 50-85 Torr. The duration of the gas etching step 130 may range from 1 to 10 minutes, 1.5 to 7 minutes, or 2 to 5 minutes. The gas flowed during the gas etching step 130 may react with the residue to form chlorine-substituted arsenic, germanium, silicon, or phosphorous, or any chlorinated derivative thereof. This can be easily purged from the reaction chamber by flowing an inert gas, such as nitrogen, argon, or krypton, for example.

FIG. 2 illustrates an exemplary reaction system 200 in accordance with at least one embodiment of the invention. The reaction system 200 comprises: a reaction chamber housing 210; a wafer holder 220 that is configured to hold a substrate 230; a first gas source 240; a second gas source 250; a third gas source 260; an inlet gas line 270; an outlet gas line 280; an exhaust 290; a pyrometer 300; and a pressure control valve 310. The first gas source 240 may be configured to flow a reaction gas used to form a film on the substrate 230. The second gas source 250 may be configured to flow another reaction gas used to form a film on the substrate 230 or may be configured to flow a purge gas. The third gas source 260 may be configured to flow an etchant gas.

The gases from the first gas source 240, the second gas source 250, and the third gas source 260 may flow through the inlet gas line 270 into the reaction chamber housing 210. Any remaining gas may be purged out through the outlet gas line 280 into the exhaust 290. Additional gas sources may be employed with additional inlet gas lines. Likewise, additional exhausts may be employed with additional outlet gas lines.

The pyrometer 300 may be embedded in the reaction chamber housing 210. The pyrometer 300 may be configured to measure a temperature within the reaction chamber housing 210. The pressure control valve 310 may be configured to control the pressure within the reaction chamber housing 210.

Running of the processes described above may improve the functioning of the pyrometer 300 and the pressure control valve 310. Both the pyrometer 300 and the pressure control valve 310 may have its performance adversely affected by accumulation of films during a film deposition process. Cleaning processes such as the one shown in FIG. 1 may remove coating, which otherwise would impede accurate readings from the pyrometer 300 and the pressure control valve 310. The cleaning process is also able to remove coating in the exhaust foreline 280 which may extend the on-tool lifetime of the foreline components 280 or enable safe disassembly of foreline components 280.

The particular implementations shown and described are illustrative of the invention and its best mode and are not intended to otherwise limit the scope of the aspects and implementations in any way. Indeed, for the sake of brevity, conventional manufacturing, connection, preparation, and other functional aspects of the system may not be described in detail. Furthermore, the connecting lines shown in the various figures are intended to represent exemplary functional relationships and/or physical couplings between the various elements. Many alternative or additional functional relationship or physical connections may be present in the practical system, and/or may be absent in some embodiments.

It is to be understood that the configurations and/or approaches described herein are exemplary in nature, and that these specific embodiments or examples are not to be considered in a limiting sense, because numerous variations are possible. The specific routines or methods described herein may represent one or more of any number of processing strategies. Thus, the various acts illustrated may be performed in the sequence illustrated, in other sequences, or omitted in some cases.

The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various processes, systems, and configurations, and other features, functions, acts, and/or properties disclosed herein, as well as any and all equivalents thereof. 

What is claimed is:
 1. A method for in-situ cleaning a reaction chamber, comprising: pre-coating a plurality of walls within a reaction chamber with a protective coating gas, the protective coating gas comprising at least one of: dichlorosilane (DCS), silane, or disilane; heating the reaction chamber to a temperature exceeding 700° C.; and flowing an etchant gas into the reaction chamber; wherein the etchant gas removes a residue from the plurality of walls, the residue comprising at least one of: arsenic-based material, germanium-based material, silicon-based material, or phosphorous-based material.
 2. The method of claim 1, wherein the etchant gas comprises at least one of: chlorine (Cl₂) or nitrogen (N₂).
 3. The method of claim 1, further comprising at least one part within the reaction chamber, wherein the part comprises at least one of: silicon carbide or graphite.
 4. The method of claim 1, wherein a pressure of the reaction chamber during the flowing step ranges between 40-100 Torr, 45-90 Ton, or 50-85 Torr.
 5. The method of claim 1, wherein the flowing step has a duration ranging from 1 to 10 minutes, 1.5 to 7 minutes, or 2 to 5 minutes.
 6. The method of claim 1, wherein a temperature of the reaction chamber during the heating step exceeds 800° C.
 7. The method of claim 1, wherein a temperature of the reaction chamber during the heating step exceeds 900° C.
 8. The method of claim 1, wherein the heating step has a duration exceeding 160 s.
 9. The method of claim 1, wherein the heating step has a duration exceeding 170 s.
 10. The method of claim 1, wherein the heating step has a duration exceeding 180 s.
 11. The method of claim 1, wherein the residue comprises an arsenic-based material.
 12. The method of claim 11, wherein removing the residue reduces a concentration of arsenic-based material to a level of 0.005 parts per million.
 13. The method of claim 2, wherein the etchant gas comprises chlorine.
 14. The method of claim 13, wherein removing the residue reduces a concentration of chlorine to a level of 0.5 parts per million.
 15. A semiconductor film deposition system comprising: a reaction chamber; a first gas source; a second gas source; an exhaust; a pyrometer configured to measure a temperature within the reaction chamber; a pressure control valve configured to modulate a pressure within the reaction chamber; and an etchant gas source; wherein the semiconductor film deposition system is configured to perform the method of claim
 1. 16. The system of claim 15, wherein the reaction chamber comprises quartz.
 17. The system of claim 15, further comprising a part disposed within the reaction chamber, the part comprising at least one of: silicon carbide or graphite. 